The catastrophic earthquake of April 25, 2015, in Nepal: Analysis of seismological data

Abstract

The paper analyzes available seismic data of the Geophysical Survey of the Russian Academy of Sciences on the catastrophic earthquake with Ms = 7.9 occurred in Nepal on April 25, 2015. It is shown that this earthquake (also called Gorkha) in its coseismic stage reflected the dynamic situation in the collision zone between the Indian and Eurasian plates, and occurred in the area of the Main Frontal Thrust in the Himalayas. In the last 15 years, the seismicity of this area has demonstrated the features of strong earthquake preparation. The study results are presented for the early postseismic stage (in the first month after the mainshock). It is found that the pattern of a decrease in aftershock activity is similar to that obtained by Tatevossian and Aptekman (2008) for the world’s earthquakes with M > 8. It is regular in the first 11–16 days and can be described by the Omori law, whereas on 17th day after the mainshock, the exponent characterizing the rate of change in the flow of events becomes to irregular. The spatial and temporal distribution of aftershocks of the 2015 Gorkha earthquake qualitatively and quantitatively indicates the heterogeneity of a seismogenic interface of the Himalayan arc collision zone between the Indian and Eurasian plates.